x86/platform/UV: Fix panic with missing UVsystab support

Fix the panic where KEXEC'd kernel does not have access to EFI runtime
mappings.  This may cause the extended UVsystab to not be available.
The solution is to revert to non-UV mode and continue with limited
capabilities.

Signed-off-by: Mike Travis <[email protected]>
Reviewed-by: Russ Anderson <[email protected]>
Reviewed-by: Alex Thorlton <[email protected]>
Acked-by: Dimitri Sivanich <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

1 files changed, 16 insertions, 8 deletions

diff --git a/arch/x86/kernel/apic/x2apic_uv_x.c b/arch/x86/kernel/apic/x2apic_uv_x.c
index 35690a168cf7..43930787cab9 100644
--- a/arch/x86/kernel/apic/x2apic_uv_x.c
+++ b/arch/x86/kernel/apic/x2apic_uv_x.c
@@ -1172,19 +1172,25 @@ static void __init decode_gam_rng_tbl(unsigned long ptr)
 		index, _min_socket, _max_socket, _min_pnode, _max_pnode);
 }
 
-static void __init decode_uv_systab(void)
+static int __init decode_uv_systab(void)
 {
 	struct uv_systab *st;
 	int i;
 
+	if (uv_hub_info->hub_revision < UV4_HUB_REVISION_BASE)
+		return 0;	/* No extended UVsystab required */
+
 	st = uv_systab;
-	if ((!st || st->revision < UV_SYSTAB_VERSION_UV4) && !is_uv4_hub())
-		return;
-	if (st->revision != UV_SYSTAB_VERSION_UV4_LATEST) {
-		pr_crit(
+	if ((!st) || (st->revision < UV_SYSTAB_VERSION_UV4_LATEST)) {
+		int rev = st ? st->revision : 0;
+
+		pr_err(
 		"UV: BIOS UVsystab version(%x) mismatch, expecting(%x)\n",
-			st->revision, UV_SYSTAB_VERSION_UV4_LATEST);
-		BUG();
+			rev, UV_SYSTAB_VERSION_UV4_LATEST);
+		pr_err(
+		"UV: Cannot support UV operations, switching to generic PC\n");
+		uv_system_type = UV_NONE;
+		return -EINVAL;
 	}
 
 	for (i = 0; st->entry[i].type != UV_SYSTAB_TYPE_UNUSED; i++) {
@@ -1205,6 +1211,7 @@ static void __init decode_uv_systab(void)
 			break;
 		}
 	}
+	return 0;
 }
 
 /*
@@ -1373,7 +1380,8 @@ void __init uv_system_init(void)
 	map_low_mmrs();
 
 	uv_bios_init();			/* get uv_systab for decoding */
-	decode_uv_systab();
+	if (decode_uv_systab() < 0)
+		return;			/* UVsystab problem, abort UV init */
 	build_socket_tables();
 	build_uv_gr_table();
 	uv_init_hub_info(&hub_info);